I recently began a project of segmenting my LAN into various VLANs. One issue that cropped up had me banging my head against the wall for days. I had a particular VM that would use OpenVPN to a private VPN provider. I had that same system sending things to a file share via transmission-daemon.
Pre-subnet move everything worked, but once I moved my file server to a different subnet suddenly this VM could not access it while on the VPN. Transmission would hang for some time before finally saying
transmission-daemon.service: Failed with result 'timeout'.
The problem was since my file server was on a different subnet, it was trying to route traffic to it via the default gateway, which in this case was the VPN provider. I had to add a specific route to tell the server to use my LAN network instead of the VPN network in order to restore connectivity to the file server (thanks to this site for the primer.)
I had to create a file
/etc/sysconfig/network-scripts/route-eth0 and give it the following line:
192.168.2.0/24 via 192.168.1.1 dev eth0
This instructed my VM to get to the 192.168.2 network via the 192.168.1.1 gateway on eth0. Restart the network service (or reboot) and success!